Garage floors make your garage beautiful. Clean, smooth concrete invites people out of their cars and into home. However, some times your concrete isn’t smooth. It develops pits and cracks, and it can also get pop-outs. Most people know what cracks and pits are, but “pop-outs,” while a common defect in garage floors, are not known as well. So let’s cover what a “pop-out” is.

“Pop-outs” are cone-shaped pieces of concrete that separate from the rest of the flooring material. They leave cone-shaped holes in your garage floor. These holes are normally anywhere from a quarter of an inch to 2 inches in diameter. There have been some pop-outs that are a foot in diameter, though those are not the rule.

The problem usually stems from porous and moisture-susceptible aggregates (which is what gravel is called when it is added to concrete) in the concrete mix. Water can get to these aggregates, either through absorption from the ground or the freezing and thawing cycle.

However the water gets into the floor, it causes the soggy material to expand. The aggregates can also expand if it freezes in wet conditions. The expansion puts pressure on the particles and on the cement matrix sitting over the aggregate. Since these aggregates can expand with serious force, the aggregate particles rupture and break off, pushing the cement over it out of the floor. If you look in the hole, you will see half of the aggregate particle that broke. You will also see the part of the aggregate that popped out on the bottom of the cone of concrete.

There is another way that pop-outs can happen. This is a chemical reaction between silica and alkalis in the cement. The alkalis make the environment very alkaline, which turns the silicas (a type of rock, frequently quartz) into a gel that absorbs water and expands forcefully. These pop-outs, called ASR pop-outs, look discolored and wet. They also tend to be small.

Regardless of the cause, water getting in the garage floor is a crucial part of the process, and so is the freezing and thawing cycle. As you can imagine, Minnesota’s tendency towards gellid winters, hot summers and rain don’t help matters much. Deicing salts used during winter on the roads can increase the damage from freezing and thawing too, leading to more pop-outs.

While most concrete installers try to avoid having the lighter, porous aggregates in their materials, the truth is that it is practically impossible to get rid of them completely. There is always a chance that chert or a similar stone has gotten in the mix, especially in local gravel. Minnesota gravel is mostly from glaciation, and aggregate gravel from that source almost always has shales, cherts, iron oxides and carbonates which are susceptible to damage from water.

Newly laid concrete is particularly inclined to absorb water, which is why you will most often see these pop-outs within the first 12 months of the floor’s life, though the ASR pop-outs can happen within the first couple of days that you have the concrete installed.

While a few pop-outs on a floor are nothing but an eye-sore, having many pop-outs can let water get deeper in the concrete. This can lead to deterioration in the floor. For instance, it can lead to the steel reinforcement in the floor corroding. Coatings of breathable, non-slip substances such as epoxy might help prevent this.

PolyTek Surface Coatings can help you avoid pop-outs, while making your garage floor beautiful with Penntek Industrial Coatings. We can also mend cracks, pits and spalling. So, if you would like to keep your floor pop-out free, contact us.